At least 100 people have been killed in an explosion at an industrial gas plant in southeast Nigeria.

The incident took place on Thursday after a gas tanker exploded as it was offloading butane cooking gas at the Chikason Group Gas plant in the town of Nnwei, Anambra State.

The casualties include the plant’s workers as well as people who lined up to refill their cooking gas cylinders in time for Christmas.

The dead and injured were transferred to the Nnamdi Azikiwe University Teaching Hospital in Nnewi, which is dominated by Christians.

Witnesses said the explosion came after the tanker began offloading gas without waiting for the prescribed cooling time.

"The fire exploded like a bomb, and the whole gas station went up in thick, black smoke amidst an explosion from cooking gas cylinders," said a witness, Emeka Peters.

"Many people were killed, and most of them were those that had been in the station queuing all day to get their cylinders refilled," he added.

Witnesses also said the explosion created a huge fire that raged for several hours.

The identity of the victims has not been released yet with reports saying they were burned beyond recognition.